Problem: Solve the system of equations. $\begin{aligned} &-7x-6y = 4 \\\\ & x=-3y+8 \end{aligned}$ $ x=$
Explanation: We are given that ${x}={-3y+8}$. Let's substitute this expression into the first equation and solve for $y$ as follows: $ \begin{aligned} -7{x}-6y &= 4\\\\ -7\cdot({-3y+8})-6y&=4\\\\ 21y-56-6y&=4\\\\ 15y&=60\\\\ y&=4 \end{aligned}$ Since we now know that ${y}={4}$, we can substitute this value in the second equation to solve for $x$ as follows: $ \begin{aligned} x &= -3\cdot{y}+8 \\\\ x&=-3\cdot{4}+8\\\\ x&=-4 \end{aligned}$ This is the solution of the system: $\begin{aligned} &x = -4 \\\\ &y=4 \end{aligned}$